Viscoelastic characteristics of short fiber reinforced polybutylene terephthalate
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Viscoelastic characteristics of short fiber reinforced polybutylene terephthalate K. Sakaue1 · M. Ochiai1 · S. Endo1 · H. Takaoka1
Received: 23 November 2018 / Accepted: 16 August 2019 © Springer Nature B.V. 2019
Abstract The mechanical characteristics of short-fiber-reinforced thermoplastics should be evaluated based on viscoelastic theory because of the time and temperature dependent characteristics of the matrix resin. In this study, the viscoelastic characteristics of short-fiberreinforced polybutylene terephthalate, PBT composite, are evaluated by material testing and micromechanics model. Firstly, tensile tests are carried out PBT composite with three fiber volume ratios under various temperature and strain rate conditions. The results show that the viscoelastic characteristics of the PBT composites can be obtained by the time-temperature superposition principle using shift factor of the PBT resin. Next, the Eshelby model combined with the Mori–Tanaka theory is used to predict to the viscoelastic characteristics of the PBT composites based on the measurement of fiber length and fiber orientation angle. The predicted viscoelastic characteristics of the PBT composites are in good agreement with the tensile test. Keywords Viscoelasticity · Composite material · Thermoplastic · Eshelby/Mori–Tanaka theory
1 Introduction Short-fiber-reinforced thermoplastics are widely used in engineering products because of the excellent specific strength and formability by injection molding. The mechanical characteristics and the strength of short-fiber-reinforced thermoplastics depend on time and temperature since thermoplastics as the matrix resin exhibit viscoelasticity. In order to evaluate the time and temperature dependent characteristics, it is necessary to conduct long-term test such as creep test. Additionally, the mechanical characteristics of composites depend on the
B K. Sakaue
[email protected]
1
Department of Mechanical Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan
Mech Time-Depend Mater
material combination of the fiber and the matrix resin, the configuration of the fiber, and the fiber volume ratio. Therefore, the selection of materials in product design needs many longterm tests. However, it is not possible to conduct the long-term tests for every composite. In order to evaluate the mechanical characteristics for various composites, it is necessary to predict the long-term behavior by accelerated test and micromechanics model. The accelerated test for polymer and polymer composites is based on time-temperature superposition principle. Many studies have showed that the master curve of creep compliance estimated by the time-temperature superposition principle can be predict the long-term creep behavior. Also, it has been showed that the master curve of strength can evaluate the long-term strength. For example, Sakai et al. investigated the creep behavior of short glass-fiber-reinforced polycarbonate and predicted the long-term creep compliance by usi
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